You have to right code after Insert A item code on line.After this insertion of A line you can right code for the insertion of b line.
[EventSubscriber(ObjectType::Table, 37, 'OnAfterInsertEvent', '', true, true)]
local procedure OnAfterInsertEventSalesLine(var Rec: Record "Sales Line")
var
SalesLine: Record "Sales Line";
LastSalesLine: Record "Sales Line";
LineNo: Integer;
begin
if Rec."No." = '1000' then begin
LineNo := 0;
LastSalesLine.Reset();
LastSalesLine.SetRange("Document Type", Rec."Document Type");
LastSalesLine.SetRange("Document No.", Rec."Document No.");
if LastSalesLine.FindLast() then
LineNo := LastSalesLine."Line No." + 10000
else
LineNo := 10000;
SalesLine.Init();
SalesLine."Document No." := Rec."Document No.";
SalesLine."Document Type" := Rec."Document Type";
SalesLine."Line No." := LineNo;
SalesLine.Insert(true);
SalesLine.Validate(Type, SalesLine.Type::Item);
SalesLine.Validate("No.", '1100');
SalesLine.Modify();
end;
end;
If you enter the 1000 item code system will auto add the 1100 item line on order according to above code.
Also you can set dynamic with adding field Sub Item No. on Item Table so system will auto create line base on the field.
see above code output as below